Checkbox with required set breaks HTML5 form validation messages in at least Chrome.

If you have a checkbox in a form that looks something like this:
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And try to submit the form before ticking the checkbox you get a HTML5 form validation error message shown (as expected), but it disappears almost immediately due to whatever manipulations on the element the event handlers attached to the checkbox by MDL are doing.

Only tested on Chrome, other browsers may behave differently given the reasons for removing the floating validation tooltip may well be browser specific.